1. Field of the Invention
The present invention relates to a color management method, wherein a Graphics Processing Unit (GPU) is used for converting colors from a source device color space to an output device color space in accordance with predetermined color profiles of the source and output devices.
The present invention further relates to a color management module and a program product embodied on a computer readable medium for implementing the method and to a printer using the method.
2. Description of Background Art
When a color image is scanned with a scanner and is then printed with a color printer, it can not be taken for granted that the colors on the printed copy will be identical with those of the original. The reason is that color processing devices such as scanners, printers and the like, operate in device dependent color spaces. The main purpose of color management is to transform one color space into another, given an input profile or source profile of the source device (e.g. scanner), an output profile of the output device (e.g. the printer) and possibly a rendering intent. The current standard for color management is set by the International Color Consortium (ICC) which has defined a format for the color profiles. For example, a color profile for a scanner may specify how the colors on an original, as defined in a standard color space such as LAB, for example, are related to the RGB colors output by the scanner. Similarly, a color profile of a printer may specify how the LAB colors that shall be visible on the printed copy are related to the CMYK color values to be input into the printer in order to achieve the desired output. In general, such a color profile is represented by two conversion tables, one mapping, for example, RGB onto LAB, and another one mapping LAB onto RGB (with suitable gamut mapping). When the scanner and the printer are combined to form a digital copier, the color managing module will perform a transformation that corresponds to concatenating the color profile of the scanner with the color profile of the printer.
Whereas color management has conventionally been the task of a CPU in a printer or other color processing device, U.S. Patent Application Publication No. 2007/0035752 A1 discloses a color management module in which at least a part of the color management operations are performed in a Graphics Processing Unit (GPU). Such a GPU is a processor with a massively parallel architecture that is typically employed in graphics cards in PCs. According to the color management method proposed in this document, the input color profile is at first linearized, if it is not linear already, and then a linear transformation, i.e. a matrix multiplication, is carried out, and, in general, a non-linear function is applied to the result in order to map the colors onto the output device color space.